Reverse rows in DecoderZlib for remoting

Windows images are upside down, so when we decode the stream and paint the
image we need to reverse the rows.

This is a temporary solution since it sets to reverse rows by default. We'll
move to use the information from the update stream to determine we should
reverse or not.

Review URL: http://codereview.chromium.org/2883055

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55314 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 31 insertions, 4 deletions

diff --git a/remoting/base/decoder_zlib.cc b/remoting/base/decoder_zlib.cc
index 3e23f95..e44a2f2 100644
--- a/remoting/base/decoder_zlib.cc
+++ b/remoting/base/decoder_zlib.cc
@@ -18,7 +18,11 @@ DecoderZlib::DecoderZlib()
       bytes_per_pixel_(0),
       updated_rects_(NULL),
       row_pos_(0),
-      row_y_(0) {
+      row_y_(0),
+      // TODO(hclam): We should use the information from the update stream
+      // to determine whether we should reverse the rows or not.
+      // But for simplicity we set to be always true.
+      reverse_rows_(true) {
 }
 
 bool DecoderZlib::BeginDecode(scoped_refptr<media::VideoFrame> frame,
@@ -106,9 +110,18 @@ bool DecoderZlib::HandleRectData(HostMessage* message) {
   const int in_size =
       message->update_stream_packet().rect_data().data().size();
   const int row_size = rect_width_ * bytes_per_pixel_;
-  const int stride = frame_->stride(media::VideoFrame::kRGBPlane);
-  uint8* out = frame_->data(media::VideoFrame::kRGBPlane) +
-      stride * (rect_y_ + row_y_) + bytes_per_pixel_ * rect_x_;
+  int stride = frame_->stride(media::VideoFrame::kRGBPlane);
+  uint8* rect_begin = frame_->data(media::VideoFrame::kRGBPlane);
+  if (reverse_rows_) {
+    // Advance the pointer to the last row.
+    rect_begin += (frame_->height() - 1) * stride;
+
+    // And then make the stride negative.
+    stride = -stride;
+  }
+
+  uint8* out = rect_begin + stride * (rect_y_ + row_y_) +
+      bytes_per_pixel_ * rect_x_;
 
   // Consume all the data in the message.
   bool decompress_again = true;
diff --git a/remoting/base/decoder_zlib.h b/remoting/base/decoder_zlib.h
index 4d20c10..05f8a99 100644
--- a/remoting/base/decoder_zlib.h
+++ b/remoting/base/decoder_zlib.h
@@ -23,6 +23,9 @@ class DecoderZlib : public Decoder {
   virtual bool PartialDecode(HostMessage* message);
   virtual void EndDecode();
 
+  // TODO(hclam): Should make this into the Decoder interface.
+  void set_reverse_rows(bool reverse) { reverse_rows_ = reverse; }
+
  private:
   bool HandleBeginRect(HostMessage* message);
   bool HandleRectData(HostMessage* message);
@@ -55,6 +58,9 @@ class DecoderZlib : public Decoder {
   // The row number in the rect that we are updaing.
   int row_y_;
 
+  // True if we should decode the image upside down.
+  bool reverse_rows_;
+
   DISALLOW_COPY_AND_ASSIGN(DecoderZlib);
 };
 
diff --git a/remoting/base/decoder_zlib_unittest.cc b/remoting/base/decoder_zlib_unittest.cc
index 8ebad1d..388abd0 100644
--- a/remoting/base/decoder_zlib_unittest.cc
+++ b/remoting/base/decoder_zlib_unittest.cc
@@ -16,13 +16,21 @@ namespace remoting {
 TEST(DecoderZlibTest, EncodeAndDecode) {
   EncoderZlib encoder;
   DecoderZlib decoder;
+  decoder.set_reverse_rows(false);
   TestEncoderDecoder(&encoder, &decoder, true);
 }
 
 TEST(DecoderZlibTest, EncodeAndDecodeSmallOutputBuffer) {
   EncoderZlib encoder(64);
   DecoderZlib decoder;
+  decoder.set_reverse_rows(false);
   TestEncoderDecoder(&encoder, &decoder, true);
 }
 
+TEST(DecoderZlibTest, EncodeAndDecodeNoneStrict) {
+  EncoderZlib encoder;
+  DecoderZlib decoder;
+  TestEncoderDecoder(&encoder, &decoder, false);
+}
+
 }  // namespace remoting